Dockerised Jenkins hangs - Openstack by Rackspace

on Rackspace Openstack (Openstack Pike version r16.0.0-beta.1) we have an issue with running an official Jenkins Docker images. Any clue what might be the problem?

Detailed info:
-once you run jenkins from the latest official image (https://github.com/jenkinsci/docker) it cannot be started properly and hangs before letting you unlock the instance as an admin
– message on the Jenkins page is “Please wait while Jenkins is getting ready to work…
Your browser will reload automatically when Jenkins is ready.”
-this issue appears only on Openstack by Rackspace (works fine on local env, google cloud platform, digital ocean)

How to reproduce:
-in your openstack project create a new instance and open ingress traffic for tcp:8080, tcp:50000
–-for Centos create a new instance from Centos 7.4 image
–-for Ubuntu create a new instance from Ubuntu 16.04.4 LTS
-associate a floating IP
-install docker
– for Centos follow https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-centos-7 (https://www.digitalocean.com/communit...)
– for Ubuntu follow https://docs.docker.com/install/linux/docker-ce/ubuntu/ (https://docs.docker.com/install/linux...) (or https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-16-04 (https://www.digitalocean.com/communit...))
-execute docker run -p 8080:8080 -p 50000:50000 jenkins/jenkins:lts
–comment: your log will finish/be dropped at
–> setting agent port for jnlp
–> setting agent port for jnlp… done-in the web browser open http://YOUR_FLOATING_IP:8080
-you will see a page which says “Please wait while Jenkins is getting ready to work…
Your browser will reload automatically when Jenkins is ready.” and there is no visible progress on the screen, no logs produced by Jenkins after that
-container is still up